R = sprandn(m,n,density,rc) also
has reciprocal condition number approximately equal to rc. R is
constructed from a sum of matrices of rank one.

If rc is a vector of length lr,
where lr <= min(m,n), then R has rc as
its first lr singular values, all others are zero.
In this case, R is generated by random plane rotations
applied to a diagonal matrix with the given singular values. It has
a great deal of topological and algebraic structure.

Tips

sprandn uses the same random
number generator as rand, randi, and randn.
You control this generator with rng.